This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A143671 #10 Apr 08 2025 10:01:41 %S A143671 10,45,150,375,750,1200,1713,2227,2492,2492,2225,2041,1575,1132,770, %T A143671 571,335,180,90,44,18,12,6,3,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, %U A143671 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 %N A143671 Number of terms in A144688 of length n. %C A143671 Since any 5-digit member of A144688 must end in 0 or 5, a(5) = 2*a(4). %C A143671 Similarly a(n) <= 2*a(n-1) for n = 6, 7, 8, 9, a(10) = a(9), and a(n) <= a(n-1) for n >= 11. %C A143671 a(n) = 0 for n > 25. %H A143671 Shyam Sunder Gupta, <a href="https://doi.org/10.1007/978-981-97-2465-9_22">On Some Special Numbers</a>, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 22, 527-565. %Y A143671 Cf. A144688. %K A143671 nonn,base %O A143671 1,1 %A A143671 _Zak Seidov_ and _N. J. A. Sloane_, Feb 08 2009